It is known to construct the framework of a building from rigidly interconnected elongate vertical and horizontal modular units, referred to hereinafter as columns and struts, which form a skeleton with wall openings designed to receive a variety of wall elements including solid walls, windows and doors. Different mountings, varying with the type of wall elements, are used to secure the latter to the skeletal framework. Thus, solid walls generally require a permanent connection whereas window panes, for example, should be removably installed to facilitate their replacement in the event of damage. Internal partitions, finally, ought to have semipermanent joints to enable an occasional rearrangement of the rooms.